linux-kernel - Re: [PATCH 06/10] x86: reduce memory and stack usage in intel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20080326065023.GG18301@elte.hu>
Date:	Wed, 26 Mar 2008 07:50:23 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Mike Travis <travis@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...e.de>
Subject: Re: [PATCH 06/10] x86: reduce memory and stack usage in
	intel_cacheinfo


* Mike Travis <travis@....com> wrote:

> * Change the following static arrays sized by NR_CPUS to
>   per_cpu data variables:
> 
> 	_cpuid4_info *cpuid4_info[NR_CPUS];
> 	_index_kobject *index_kobject[NR_CPUS];
> 	kobject * cache_kobject[NR_CPUS];
> 
> * Remove the local NR_CPUS array with a kmalloc'd region in
>   show_shared_cpu_map().

thanks Travis, i've applied this to x86.git.

one observation:

>  static ssize_t show_shared_cpu_map(struct _cpuid4_info *this_leaf, char *buf)
>  {
> -	char mask_str[NR_CPUS];
> -	cpumask_scnprintf(mask_str, NR_CPUS, this_leaf->shared_cpu_map);
> -	return sprintf(buf, "%s\n", mask_str);
> +	int n = 0;
> +	int len = cpumask_scnprintf_len(nr_cpu_ids);
> +	char *mask_str = kmalloc(len, GFP_KERNEL);
> +
> +	if (mask_str) {
> +		cpumask_scnprintf(mask_str, len, this_leaf->shared_cpu_map);
> +		n = sprintf(buf, "%s\n", mask_str);
> +		kfree(mask_str);
> +	}
> +	return n;

the other changes look good, but this one looks a bit ugly and complex. 
We basically want to sprintf shared_cpu_map into 'buf', but we do that 
by first allocating a temporary buffer, print a string into it, then 
print that string into another buffer ...

this very much smells like an API bug in cpumask_scnprintf() - why dont 
you create a cpumask_scnprintf_ptr() API that takes a pointer to a 
cpumask? Then this change would become a trivial and much more readable:

 -	char mask_str[NR_CPUS];
 -	cpumask_scnprintf(mask_str, NR_CPUS, this_leaf->shared_cpu_map);
 -	return sprintf(buf, "%s\n", mask_str);
 +	return cpumask_scnprintf_ptr(buf, NR_CPUS, &this_leaf->shared_cpu_map);

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/